With the rapid development of wireless communication services, a future network needs a layout and design with the lowest cost to support communications at a blind area or a hotspot area, for providing better coverage or a better system throughput, and therefore, a relay technology is introduced. In a common relay network, a data packet is sent from a transmitter to a receiver via a single path and through a relay station with multiple continuous hops.
In order to provide a higher data transmission rate within a broader coverage range, a cooperative relay technology is introduced. In a cooperative relay network, one or more relay stations are disposed between the transmitter and the receiver, and during data transmission process, the relay stations are cooperative with each other when transmitting a data packet in parallel. With a broadcast characteristic that a wireless channel can reach multiple relay stations simultaneously, the relay stations are enabled to work cooperatively, thus reducing power consumption for transmitting the data packet from the transmitter to the receiver, and significantly increasing gains of a total throughput and power efficiency.
Before the data transmission, pre-coding needs to be performed at the transmitter, and in the prior art, for a point-to-multipoint multi-user, a pre-coding scheme is:
A transmitter transmits a plurality of different data packets to a plurality of different receivers simultaneously through multi-antenna channels, and at this time, pre-coding at the transmitter enables different data packets to be transmitted in parallel on respective single link channels. Pre-coding information at the transmitter is obtained by calculating channel information from the transmitter to all the receivers, where the channel information is known by the transmitter; and may also be obtained by calculating feedback of all the receivers.
As shown in FIG. 1, output signals of different receivers may be represented as:
         {                                                      y              1                        =                                                                                H                    1                                    ⁢                  Ps                                +                                  n                  1                                            =                                                                    H                    1                                    ⁢                                      p                    1                                    ⁢                                      s                    1                                                  +                                  (                                                                                    H                        1                                            ⁢                                              p                        2                                            ⁢                                              s                        2                                                              +                                          n                      1                                                        )                                                                                                                                    y                2                            =                                                                                          H                      2                                        ⁢                    Ps                                    +                                      n                    2                                                  =                                                                            H                      2                                        ⁢                                          p                      2                                        ⁢                                          s                      2                                                        +                                      (                                                                                            H                          2                                                ⁢                                                  p                          1                                                ⁢                                                  s                          1                                                                    +                                              n                        2                                                              )                                                                        ,                              
where, H1 and H2 respectively are single link channel information from the transmitter to different receivers, p1 and p2 are optimal pre-coding information corresponding to different receivers, n1 and n2 are additive noise vectors on different receivers, and contents in the brackets are interference signals received by the receivers.
In the implementation of the present invention, the inventor finds that the prior art has at least the following problem.
In conventional pre-coding design directed to a point-to-multipoint transmission scenario, a transmitter transmits a plurality of different data packets to a plurality of different receivers simultaneously through multi-antenna channels. In a cooperative relay system, the transmitter needs to transmit the same data to a plurality of different receivers simultaneously, and if the transmitter still adopts the preceding method for pre-coding, each receiver cannot obtain similarly good transmission performance.